JP3381734B2 - Friction material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-asbestos friction material used as a disk pad, a brake lining, a clutch facing of automobiles, vehicles, industrial machines, etc., and particularly, it has improved water resistance. It is a friction material.

[0002]

2. Description of the Related Art Conventionally, asbestos (asbestos) is used as a reinforcing base material and a phenol resin is used as a binder resin (binder, binder).
The friction material has excellent cost performance and is used in many applications. However, the carcinogenicity of asbestos has been discovered, and asbestos is naturally discharged from the friction material using asbestos, which causes environmental pollution. Therefore, a method of substituting asbestos with glass fibers, rock fibers, steel fibers, brass fibers, aramid fibers, etc., hard carbon, curlsine coke, etc., which are more expensive than these, was studied. For example, a friction material composed of steel fibers and wholly aromatic polyamide fibers (JP-A-56-88433),
There is a friction material made of glass fiber (JP-A-51-87549).

Initially, glass fiber or steel fiber as a reinforcing base material was developed. For example, Japanese Patent Application Laid-Open No. 48-16972 proposes a method for producing clutch fading using glass fiber. Glass fiber was linear and good for clutch facings and could be used as roving.However, as a brake material, there were problems with face-to-face wear properties and friction coefficient, and in comparison with asbestos, the temporary mold retention was poor, Since it easily collapses, there are still problems with productivity, and it is now rarely used. Further, inorganic fibers, including glass fibers, may become carcinogenic like asbestos when they become ultrafine fibers having a diameter of several microns or less, and it is difficult to maintain the same productivity as ultrafine fibers as asbestos.

In the case of a semi-metallic disc brake pad having a steel fiber as a reinforcing base material, remarkable brake squeal, rust generation, high thermal conductivity, and other defects were found. On the other hand, fibers of aramid resin, which is a kind of wholly aromatic polyamide, and fibril pulp are excellent reinforcing base materials that are excellent in abrasion resistance, face-to-face aggression, and brake squeal. Is an excellent one to improve the. However, this aramid resin has a large water absorption and is poor in affinity with a binder, for example, a phenol resin, a bismaleimide / triazine resin, etc., and when rapidly heated, swelling due to water vapor occurs and the friction material peels off. It could happen. From these points,
There is a problem that the usable amount is limited, resulting in insufficient strength.

[0005]

DISCLOSURE OF THE INVENTION The present invention has found a fiber-reinforced base material which solves the above-mentioned problems of the friction material, especially the drawbacks of fibril pulp of aramid resin, and has excellent water resistance and affinity with a binder. It is to provide a good friction material having high property.

[0006]

That is, according to the present invention, in a friction material containing a fiber-reinforced base material other than asbestos, a binder and a friction and wear modifier, a part of the fiber-reinforced base material is aromatic liquid crystalline. A friction material comprising fibril pulp of polyester resin. Further, in a preferred embodiment of the present invention, the fibril pulp of the aromatic liquid crystalline polyester resin is one in which the melting start temperature is increased by heat treatment, and the melting start temperature is 300 ° C. or higher, or A friction material characterized by being infusibilized.

The structure of the present invention will be described below. First, the fibril pulp of the aromatic liquid crystalline polyester resin, which is a feature of the present invention, is composed of an aromatic liquid crystalline polyester resin, or one obtained by heat treating an aromatic liquid crystalline polyester resin to raise the melting start temperature. Is.

The aromatic liquid crystal polyester resin is a thermoplastic polymer that forms an anisotropic melt phase, and is generally classified as a thermotropic liquid crystal polymer.
In the molten state, the polymer is shear oriented. Further, if a pulverizing means is selected, the pulverization treatment can suppress the generation of powdery substances to obtain fibril pulp.

The aromatic liquid crystalline polyester resin is mainly composed of an aromatic dicarboxylic acid, an aromatic diol, an aromatic hydroxycarboxylic acid and the like, and if necessary, an alicyclic dicarboxylic acid, an alicyclic or aliphatic diol. It is produced by polycondensation using, for example. Generally, the weight average molecular weight of this polymer is in the range of 2,000 to 200,000, and the melting start temperature (transition temperature from solid state to liquid crystal state) by differential scanning calorimeter (DSC) is 250 ° C. or higher. In the present invention, those having a weight average molecular weight of 15,000 or more are preferable,
The melting start temperature by DSC is preferably 300 ° C or higher.

As such an aromatic liquid crystalline polyester resin, Zyder SRT-300 manufactured by Nippon Petrochemical Co., Ltd.,
Examples include Vectra A-950 manufactured by Polyplastics Co., Ltd. Other than ester bonds such as polyester imides described in JP-A-3-91534 and polyester amides described in JP-A-57-177019 and JP-A-57-177020. It also includes an aromatic liquid crystal polyester resin containing a bonding group of.

Further, in the present invention, it is more preferable to use a material having an improved melting start temperature by the above DSC or the like or an infusibilized material, which is appropriately heat-treated using a catalyst. Heat treatment is 0 to 30 ℃ from the melting start temperature
This is carried out by heating at a low temperature to raise the melting start temperature and, if necessary, raising the heat treatment temperature according to the raised melting start temperature.
This heat treatment may be a multi-step step treatment, or a method of continuously raising the heat treatment temperature in response to an increase in the melting start temperature. Further, from the viewpoint of increasing the molecular weight and removing monomers and the like, it is preferable to carry out this heat treatment under reduced pressure. In addition,
When producing fibril pulp by crushing or milling, it is preferable to perform the heat treatment in the state of pellets before crushing from the viewpoint of handleability, etc., but fibril pulping for each aromatic liquid crystalline polyester resin used It is better to confirm that is possible.

An example of step processing is as follows. 1. At a temperature 0 to 30 ° C. lower than the melting start temperature, 0.5
After heating for several hours, the melting start temperature is increased by about 5 to 30 ° C. 2. Raise the heat treatment temperature substantially corresponding to the melting start temperature raised in 1. above, and heat treat in the same manner. 3. Raise the heat treatment temperature to a temperature approximately corresponding to the melting start temperature raised by the heat treatment just before, and repeat the heat treatment as appropriate.

In this heat treatment, 1. The melting start temperature rises and the heat resistance improves. 2. The molecular weight increases. 3. Monomers and oligomers are removed by volatilization, polymerization, etc. In particular, the effect of removing monomers and oligomers in 3. is that hydroxyl groups and carboxyl groups are reduced, and therefore excessive reaction of the thermosetting resin used as a binder can be suppressed. It is preferable from the point.

Although the infusibilization of the aromatic liquid crystalline polyester resin may occur only by the above heat treatment, the above heat treatment is appropriately performed in combination with a catalyst to greatly increase the degree of polymerization and to grow crystals. Or by introducing a cross-linking structure between the molecules,
For example, a homopolymer of p-hydroxybenzoic acid is an infusible polymer due to an increase in the degree of polymerization.
7358 describes infusibilization with the combined use of catalysts.

The fibril pulp of the present invention is usually produced by grinding or pulverizing pellets with a wet pulverizer or a dry crushing pulverizer combined with air flow. The fibers are produced by melt spinning and the fibrils are produced. -Pulping method may be used. In the case of grinding or milling, a wet mill is suitable. This method uses a small diameter pellet of an aromatic liquid crystalline polyester resin having a diameter of 1 mm or less or an ordinary pellet coarsely crushed to have a diameter of 1 mm or less, and put it into a grinder with water, and grind it into a slurry state. The resulting fibril-pulp mixed solution is dehydrated and separated by a centrifuge and further dried.

The present invention is characterized in that the fibril pulp of the above-mentioned aromatic liquid crystalline polyester resin is used as a part of the fiber reinforced substrate, and the binder (binder composition) and other asbestos are used. As for the fibrous reinforcing base material and the friction / wear modifier to be removed, conventional materials can be appropriately used.

Binder (binder, binder composition)
As, phenolic resins, cyanate ester resins
(USP-4,944,373), other friction materials for brakes, NBRs, resins for clutch fading such as melamine modified phenolic resins, etc., and cyanate ester resins containing polycyclic aromatic pitch, phenol modified aromatics Aromatic hydrocarbon formaldehyde resin novolac / epoxy resin, phenol-modified aromatic hydrocarbon formaldehyde resin novolac / epoxy resin / cyanate ester resin composition, etc. are mentioned, and a curing catalyst, mold release agent, etc. are appropriately added. It is possible.

Examples of the fibrous reinforcing substrate other than asbestos include inorganic or metal fibers, specifically, steel fiber, steel fiber having a Fe ₃ O ₄ film formed on the surface, copper or copper alloy fiber, and CuO on the surface. Examples include film-formed copper fibers, carbon fibers with a final firing temperature of 1100 ° C or less, rock wool, ceramics fibers, and potassium titanate fibers.
Used in combination with more than one species. Rock wool fiber, steel fiber, copper fiber, final firing temperature
It is preferable to mainly use carbon fibers having a temperature of 1100 ° C. or less (not completely graphitized).

Further, these fibrous reinforcing base materials may be appropriately surface-treated with a cyanate ester resin used as a component of the above-mentioned binder composition, or a steel having a Fe ₃ O ₄ film formed on the surface thereof. Cu on fibers and surfaces
A copper fiber having an O film formed thereon can be suitably used after being appropriately treated to have a more stable surface.

As the friction and wear modifier, barium sulfate,
Hardened resin powder such as graphite, calcium carbonate, molybdenum disulfide, calcium fluoride, BT resin dust, alumina, silica, glass short fiber, rock wool short fiber, mullite, copper, brass, bronze, iron, zinc, tin Examples include metal powders and chips, such as copper oxide, antimony trioxide, zirconium oxide, ferric oxide, etc., stabilizing the friction coefficient from low temperature to high temperature, imparting wear resistance, and preventing high temperature fade. It is achieved by appropriately combining functions such as cleaning of the disk surface.

The BT resin dust is a phenol-modified aromatic hydrocarbon formaldehyde resin novolak obtained by epoxidizing a phenol-modified aromatic hydrocarbon formaldehyde resin novolak obtained by reacting an aromatic hydrocarbon-formaldehyde resin with phenols. -It is made by curing and crushing a mixture of epoxy resin and BT resin.

The friction material of the present invention is manufactured using the above components. As this method, the composition for the friction material is appropriately
Blender, Eirich mixer, Banbury mixer, Ledike mixer, Henschel mixer, etc. method of mixing, prepared by uniformly mixing by other means, arrange this in a mold of the desired shape, etc., A general method is preforming and heating / pressurizing. In addition to this, when burst strength is required,
As a fibrous reinforcing base material, a bulky processed strand is usually used, and other components are attached to the strand to produce a preform yarn, which is arranged in a desired shape by a spiral woven method or the like, and preformed. Then, there is a method of placing in a mold or the like, preforming, and heating / pressurizing. A method of using a material obtained by cutting the preform yarn to a size of several centimeters or less as a molding material can also be appropriately used.

[0023]

EXAMPLES The present invention will be described below with reference to examples. The "parts" and "%" in the examples are based on weight unless otherwise specified. Example 1 To 100 parts of cyanate-maleimide resin (BT-2480 manufactured by Mitsubishi Gas Chemical Co., Inc., powder 120 mesh pass), 0.3 parts of acetylacetone iron and 0.5 part of dicumyl peroxide were added as a catalyst, and the mixture was placed in a ball mill. And uniformly pulverized and mixed to produce a binder masterbatch.

Aromatic liquid crystalline polyester resin (p-hydroxybenzoic acid, hydroquinone, 2,6-naphthalenedicarboxylic acid, N, N '-(4,4'-diphenylether) -bis-3,4-dicarboximide benzoic acid Melting start temperature with acid as monomer
290 ℃ / 1 hour +
After a step heat treatment of 310 ° C./30 minutes + 330 ° C./30 minutes, the mixture was ground with a wet grinder to separate water, and dried to obtain fibril pulp.

Disc brakes using the following ingredients
We manufacture a molding material for pads and use it to
Preformed at kgf / cm ² . The obtained preformed product had a desired shape during the operations such as transfer and mold injection.・ Binder masterbatch 20 parts ・ Aromatic liquid crystalline polyester resin fibrils ・ pulp 10 parts ・ Rock wool fibers 15 parts ・ Brass fibers 15 parts ・ Barium sulfate 20 parts ・ Graphite 15 parts ・ BT resin dust * 1 5 parts Note) * 1: 20 to 100 mesh powder consisting of a cured product of phenol-modified xylene, formaldehyde resin novolac, epoxy resin / BT resin = 7: 3.

After punching, the surface is processed by the sand shot method, and the iron plate on which the adhesive layer is formed is set in a mold, and the above-mentioned preform is laid on top of it and pressed.
After press molding at 200kgf / cm ² and temperature 175 ℃ for 10 minutes,
It was taken out of the mold and subjected to atto-curing at 180 ° C / 3 hours + 270 ° C / 4 hours to obtain a disc brake pad. The test results obtained using this disc brake pad are shown in Tables 1 and 2.

Comparative Example 1 The same procedure as in Example 1 was carried out except that fibril pulp of aramid resin was used instead of fibril pulp of aromatic liquid crystalline polyester resin. The results are shown in Tables 1 and 2.

Example 2 To 100 parts of cyanate-maleimide resin (manufactured by Mitsubishi Gas Chemical Co., Inc., BT-2480, powder 120 mesh pass), 0.3 parts of acetylacetone iron and 0.5 part of dicumyl peroxide were added as catalysts. Further, 20 parts of phenol-modified xylene-formaldehyde resin novolac-epoxy resin (manufactured by Mitsubishi Gas Chemical Co., Inc., Nikanol GP-200GE) was added, and the mixture was uniformly pulverized and mixed in a ball mill to produce a binder masterbatch.

A friction material molding material was manufactured by uniformly mixing the binder masterbatch prepared above and the following components.・ Binder masterbatch 10 parts ・ Steel fiber 50 parts ・ Copper fiber 15 parts ・ Barium sulfate 10 parts ・ Graphite 10 parts ・ BT resin ・ dust 5 parts

Further, the following components were uniformly mixed to produce a molding material for a heat insulating layer. -Binder master batch 15 parts-Steel fiber 25 parts-Copper fiber 10 parts-Barium sulfate 20 parts-Graphite 10 parts-Aromatic liquid crystalline polyester resin fibril pulp * 2 15 parts-BT resin dust * 2 5 parts * 2: Same as Example 1

A preforming die was charged with 20 parts of the above-prepared molding material for the heat insulating layer and then 80 parts of the friction material molding material, and preformed at a surface pressure of 50 kgf / cm ² . After punching, the surface is processed by the sand shot method, and the adhesive (cyanate ester / maleimide resin adhesive composition solution (Mitsubishi Gas Chemical Co., Ltd., BT-A304) is applied and dried, An iron plate with an adhesive layer was manufactured.

This iron plate is set in a mold, and the above-mentioned preform is placed on the heat insulating layer side with the heat insulating layer side being the iron plate side.
After press-molding at a temperature of 200 ° C and a pressure of 200 kgf / cm ² for 10 minutes, it was taken out of the mold and subjected to atto-curing in an oven at a temperature of 230 ° C for 8 hours to obtain a semi-metallic disc brake pad. The test results obtained using this disc brake pad are shown in Tables 1 and 2. Japanese Industrial Standard JIS D 441
1 The friction coefficient was measured by the test method.In the abrasion test, the pad with the brake friction material attached to the disc rotor set at a temperature of 550 ° C was used for inertia moment 5 kgf ms ² , braking initial speed 160 km / H, braking This is the result of observing the rotor surface after measuring the wear amount of the friction material after a braking test with a deceleration of 0.6 G and a braking frequency of 200 times.

[0033]

[Table 1] Friction coefficient (μ) After humidification test * 1 Measurement temperature 100 ℃ 150 ℃ 200 ℃ 250 ℃ 300 ℃ 100 ℃ 200 ℃ Example 1 0.42 0.43 0.42 0.41 0.40 0.38 0.33 Comparative example 1 0.43 0.42 0.40 0.40 0.39 0.33 Occurrence Example 2 0.47 0.48 0.45 0.43 0.43 0.43 0.40 * 1: After holding at 40 ° C, 95% RH for 48 hours

[0034]

[Table 2]

Example 3 A strand having an apparent diameter of 3 mm formed by converging E-glass monofilaments having a fiber diameter of 6 μm, which had been previously treated with a silane coupling agent, was immersed in a methanol solution of a melamine-modified phenol resin having a concentration of 15%. A pre-impregnated strand was manufactured by drying at a temperature of 120 ° C for 1 hour.

After dissolving NBR in toluene and further adding a melamine-modified phenol resin, the viscosity is 10,000 to 20,000.
High viscosity solution of cps, sulfur, zinc oxide and crosslinking accelerator
A rubber cross-linking agent composed of (CZ) and fibril pulp of barium sulfate, carbon, and aromatic liquid crystalline polyester resin were kneaded and mixed. This kneaded material was attached to the pre-impregnated strand prepared above, wrapped with brass fibers, and sufficiently air dried to produce a preform yarn.

Using the preformed yarn produced above, it was arranged in a disk shape by the spiral woven method, set in a mold and pre-pressed, and then the temperature was 150 ° C. and the surface pressure was 200 kgf / cm. ^{It was} heated and pressed at ^{2 for} 10 minutes. The obtained molded product was taken out of the mold, heat-treated at 200 ° C. for 8 hours in a heating furnace, and the front and back surfaces of a desired friction surface were polished to obtain a disk-shaped clutch facing.

Table 3 shows the result of the test using this clutch facing. The obtained clutch facing contained the following components.・ Glass fiber 40 parts ・ Brass fiber 4 parts ・ Melamine modified phenolic resin 12 parts ・ NBR 14 parts ・ Rubber cross-linking agent 6 parts ・ Barium sulfate 8 parts ・ Graphite 8 parts ・ Aromatic liquid crystalline polyester resin fibrils ・ Pulp * 2 8 Part * 2: Same as Example 1

Comparative Example 2 Table 3 shows the same results as in Example 3, except that the fibril pulp of the aramid resin was used in place of the fibril pulp of the aromatic liquid crystalline polyester resin.

Example 4 A strand having an apparent diameter of 3 mm obtained by converging E-glass monofilament having a fiber diameter of 6 μm which had been previously treated with a silane coupling agent and fibril pulp of an aromatic liquid crystalline polyester resin was bulk processed. This strand is 2,2-bis (4-cyanatophenyl) propane / N, N'-bismaleimidophenylmethane = 95/5 cyanate ester-maleimide resin
(Hereinafter referred to as BT-2060B) was immersed in a methyl ethyl ketone solution having a concentration of 10%, and then dried at 120 ° C. for 30 minutes to obtain a pre-impregnated strand.

Barium sulfate, carbon, and BT resin dust were added to the same BT-2060B as above to prepare a highly viscous solution having a concentration of 80%, and this was adhered to the pre-impregnated strand obtained above. It was dried at ℃ for 15 minutes, wrapped with a brass fiber having a diameter of 0.2 mm, and sufficiently dried in air to produce a preform yarn having a diameter of about 4.0 mm.

Using the preformed yarn produced above, it was arranged in a disk shape by the spiral woven method, set in a mold, pre-pressed, and then at a temperature of 180 ° C.
It was heated and pressed at a surface pressure of 200 kgf / cm ^{2 for} 15 minutes. Take out the obtained molded product from the mold and put it in a heating furnace at 150 ° C for 1 hour +
A stepwise heat treatment was performed at 240 ° C for 6 hours, and the front and back surfaces of the desired friction surface were polished to obtain a disk-shaped clutch facing.

The resulting clutch facings contained the following components.・ 40 parts of glass fiber ・ fibril of aromatic liquid crystalline polyester resin ・ Pulp * 2 6 parts ・ BT-2060B 25 parts ・ Barium sulfate 10 parts ・ Carbon 10 parts ・ BT resin dust * 2 5 parts ・ Brass fiber 4 parts * 2: The same test results as in Example 1 were used and the results of the tests were shown in Table 3.

[0044]

[Table 3] Friction coefficient (μ) Abrasion rate * 2 After humidification test * 1 Measurement temperature 50 ℃ 100 ℃ 200 ℃ 300 ℃ 100 ℃ 200 ℃ 300 ℃ Example 3 0.41 0.42 0.37 0.28 0.36 0.34 8.3 Comparative example 2 0.43 0.41 0.34 0.20 0.39 Blistering 10.1 Example 4 0.45 0.44 0.42 0.39 0.40 0.39 1.7 * 1: 40 ℃, 95% RH, after holding for 48 hours * 2: Unit: × 10 ^-7 cm ³ kgf ^-1 m ^-1

[0045]

As is clear from the above detailed description of the invention and the examples, the friction material of the present invention uses the fibril pulp of the aromatic liquid crystalline polyester resin, so that It has excellent affinity, heat resistance, and other general performance, as well as low water absorption,
Swelling due to heat when the temperature rises due to moisture absorption and other abnormalities have been remarkably improved. In addition, it is also excellent in shape retention by temporary molding, and has an extremely high industrial significance.

Claims (4)

(57) [Claims] 1. A friction material comprising a fiber-reinforced base material other than asbestos, a binder and a friction and wear modifier, wherein a part of the fiber-reinforced base material contains fibril pulp of an aromatic liquid crystalline polyester resin. Characteristic friction material 2. The friction material according to claim 1, wherein the fibril pulp of the aromatic liquid crystalline polyester resin is formed by raising the melting start temperature by heat treatment. 3. The friction material according to claim 1, wherein the fibril pulp of the aromatic liquid crystalline polyester resin has a melting start temperature of 300 ° C. or higher. 4. The friction material according to claim 1, wherein the fibril pulp of the aromatic liquid crystal polyester resin is infusibilized.